MIG Welding: The Basics for Mild Steel

MIG welding is the most common welding process. It is a process that joins two materials together using a solid wire electrode that is being fed through a welding gun and then into the weld pool. To protect the weld pool from contamination, a shielding gas is used for welding gun. MIG means Metal Inert Gas. Technically, it is called Gas Metal Arc Welding or simply Wire Welding.

The MIG welding process allows DIY welder or anyone to make various types of fabrication and to repair welds. Due to its flexibility and its popularity as an easy process, it has become common to many people. Some people even consider it as easy as using a glue gun. Although it is not that simple in reality, it could be an easy task for expert or professional welders by just following the basic steps.

1.Ensure safety first before you start steel welding

Before anything else, one should ensure protection by wearing proper safety apparel. Among these apparel are as follows:

One should ensure that he wears the best and proper apparel before beginning the any welding task. Additionally, one should ensure that there are no flammable things within the area.

2.Prepare the steel before welding process

Use a metal brush to clean the metal. It should be clean before it strickes the arc to avoid negative wire feeding performance. Solid MIG wire does not have high resistance when it comes to rust, dirt and oil unlike stick and flux cored electrodes which can tolerate such contaminants. So make sure, the MIG wire is clean. Bevel the joint of thicker metal to ensure that the weld passes through the base metal.

3.Prepare the equipment needed

Now that you are ready and you have cleaned metal you will use. It’s time for you to prepare the equipment you need for this process.

Make sure you check the cables you will use before striking an arc. Make sure the cable connections are free from damages. If there are damages seen, make sure to replace them right away.

MIG welding needs DC electrode positive or reverse polarity. You will find the polarity connections inside the machine. Make sure to select electrode polarity before you begin.

Turn the shielding gas on for the gas to flow. Set it to a rate of 20 to 25 cubic feet per hour. If you think there are any leaks, dispose the hose immediately and replace it with a new one.

Adjust the equipment according to the manual. Check if you are using the correct tension. Inaccurate or wrong tension will lead to poor wire feeding performance.

Discard the wire if it looks rusty or if it has defects.

4.Select the right wire for your project

Keep in mind that if you are going to weld a thin material, you should use a wire that has a diameter of .023-in to reduce heat input. On the other hand, if you are going to weld a thick material, you should use a wire that has a diameter of .035-in. There are two common wire types for steel. One is AWS classification ER70S-3 which is for all-purpose welding while ER70S-6 is for dirty or rusty steel. This type of wire has deoxiders that are needed in welding dirty steel.

5.Select the right blend of gas

75/25 or C25 is appropriate for all purpose shielding gas for carbon steel. It has 75% argon and 25% carbon dioxide. This blend produces little amount of spatter, it doesn’t create burn-through on metals and it has good bead appearance. Using 100% carbon dioxide increases spatter, makes the bead rougher but provides deeper penetration.

6.Know the amount of voltage and amperage the weld needs

Choosing the right amount of voltage and amperage is based on different variables which include thickness and type of metal, shielding gas and wire diameter. Miller simplified setting proper voltage and amperage using two tools. There are:

A chart placed inside the door housing of a wire feed system

Auto-Setä function by Miller that is found on four Millermatic models.

Both tools are helpful to determine the right amount of voltage and amperage for the weld.

7.Stick-out of the wire

Make sure you maintain a stick out of 3/8 in. Check if there is a sizzling bacon sound produced. If the arc creates an irregular sound, it could be because of the length of stick-out is too long resulting to errors.

8.Backhand or forehand technique

Forehand technique (push technique) is pushing the gun away from the puddle, which produces lower penetration and wider bead. Backhand technique (pull technique points back the welding gun at the weld puddle and away from the metal. This produces deeper penetration and narrower bead.

9.Travel Angle and work angle

Travel angle is the angle of the gun placed in perpendicular position. Commonly among normal welding is a travel angle of 5-15 degrees. Beyond that creates more spatter and lower penetration. On the other hand, work angle is the position of the welding joint.

Butt weld – 180 degree joint.

T-join – 90 degree joint.

Lap joint – 60-70 degree join.

10.Horizontal, vertical and overhead positions

Horizontal positions: The gun angle must be slightly dropper by 0-15 degrees due to the effects of gravity. If the work angle is not changed, it may result to a saggy filler metal.

Vertical position: This position can be difficult. The voltage and amperage should be decreased to 10-15%. This helps because it avoids excessive met-through.

Overhead position: This a technique that involves dragging or pushing gun techniques. But due to gravity, travel speed must be fast enough so that the metal will not fall out of the joint.